The Glicko-2 rating system is a method for assessing a player's strength in games of skill, such as chess and go.
The algorithm is explained by its author, Mark E. Glickman, on http://glicko.net/glicko.html.

Each player begins with a rating, a rating deviation (accuracy of the rating) and a volatility (speed of rating evolution). These values will evolve according to the outcomes of matches with other players.

You should not update the ranking after each match.
The typical use of glicko is to calculate the ratings after each tournament (ie collection of matches in a period of time).
A player rating will evolve after a tournament has finished, but not during the tournament.

You can see a client side javascript example using tournaments here : https://github.com/mmai/glicko2js/blob/master/example/index.html

Here is what says Mark E. Glickman about the number of matches in a tournament or rating period (cf. http://www.glicko.net/glicko/glicko2.pdf ) :

The Glicko-2 system works best when the number of games in a rating period is moderate to large, say an average of at least 10-15 games per player in a rating period.